An additional function of the rough endoplasmic reticulum protein complex prolyl 3-hydroxylase 1·cartilage-associated protein·cyclophilin B: the CXXXC motif reveals disulfide isomerase activity in vitro

J Biol Chem. 2013 Nov 1;288(44):31437-46. doi: 10.1074/jbc.M113.498063. Epub 2013 Sep 16.


Collagen biosynthesis occurs in the rough endoplasmic reticulum, and many molecular chaperones and folding enzymes are involved in this process. The folding mechanism of type I procollagen has been well characterized, and protein disulfide isomerase (PDI) has been suggested as a key player in the formation of the correct disulfide bonds in the noncollagenous carboxyl-terminal and amino-terminal propeptides. Prolyl 3-hydroxylase 1 (P3H1) forms a hetero-trimeric complex with cartilage-associated protein and cyclophilin B (CypB). This complex is a multifunctional complex acting as a prolyl 3-hydroxylase, a peptidyl prolyl cis-trans isomerase, and a molecular chaperone. Two major domains are predicted from the primary sequence of P3H1: an amino-terminal domain and a carboxyl-terminal domain corresponding to the 2-oxoglutarate- and iron-dependent dioxygenase domains similar to the α-subunit of prolyl 4-hydroxylase and lysyl hydroxylases. The amino-terminal domain contains four CXXXC sequence repeats. The primary sequence of cartilage-associated protein is homologous to the amino-terminal domain of P3H1 and also contains four CXXXC sequence repeats. However, the function of the CXXXC sequence repeats is not known. Several publications have reported that short peptides containing a CXC or a CXXC sequence show oxido-reductase activity similar to PDI in vitro. We hypothesize that CXXXC motifs have oxido-reductase activity similar to the CXXC motif in PDI. We have tested the enzyme activities on model substrates in vitro using a GCRALCG peptide and the P3H1 complex. Our results suggest that this complex could function as a disulfide isomerase in the rough endoplasmic reticulum.

Keywords: Collagen; Collagen Biosynthesis; Disulfide; Endoplasmic Reticulum (ER); Oxidation-Reduction; Prolyl 3-Hydroxylase; Protein Isomerase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Animals
  • Chickens
  • Cyclophilins / chemistry*
  • Cyclophilins / genetics
  • Cyclophilins / metabolism
  • Endoplasmic Reticulum, Rough / chemistry*
  • Endoplasmic Reticulum, Rough / genetics
  • Endoplasmic Reticulum, Rough / metabolism
  • Extracellular Matrix Proteins / chemistry*
  • Extracellular Matrix Proteins / genetics
  • Extracellular Matrix Proteins / metabolism
  • Humans
  • Membrane Glycoproteins / chemistry*
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / metabolism
  • Mice
  • Molecular Chaperones
  • Multiprotein Complexes / chemistry*
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism
  • Peptides / chemistry
  • Peptides / genetics
  • Peptides / metabolism
  • Prolyl Hydroxylases
  • Protein Disulfide-Isomerases / chemistry*
  • Protein Disulfide-Isomerases / genetics
  • Protein Disulfide-Isomerases / metabolism
  • Protein Structure, Quaternary
  • Protein Structure, Tertiary
  • Proteins / chemistry*
  • Proteins / genetics
  • Proteins / metabolism
  • Proteoglycans / chemistry*
  • Proteoglycans / genetics
  • Proteoglycans / metabolism


  • CRTAP protein, human
  • Crtap protein, mouse
  • Extracellular Matrix Proteins
  • Membrane Glycoproteins
  • Molecular Chaperones
  • Multiprotein Complexes
  • Peptides
  • Proteins
  • Proteoglycans
  • cyclophilin B
  • Prolyl Hydroxylases
  • P3H1 protein, human
  • Cyclophilins
  • Protein Disulfide-Isomerases